Washing of sand, gravel, and the like



Jun 16, 1942. J. o. SAMUEL 2,286,979

WASHING OF SAND, GRAVEL, AND THE LIKE Filed June 24, 1941.

Patented June 16, 1942 WKS I I ING GF S A ND, GEAVEL, AND THE'LIKE John" Oswald Samuel, Swansea, Wales, assignor to 'Unifloc Reagents Limited, Swansea, Wales, a

British company 'AfipIiGatiOn'JiineM, 1941, v

InGreat Britain June '17,

7 Claims.

This invention'is 'for improvements inor' relating to the washing'ofsa'nd; gravel and the like. This application corresponds "to British applicationNo. 10497740 "filed June '17, 1940.

It is an obj'ectb'f th e present invention to clean sand, e; gffoundrysan'd," gravel or the like "and to free them from impurities with which theymay'be'associated. Inthe'case of sand or "gravel-these impuritiesimayinclude finely divided clay andotherfinesoccurring with the sand and 'initsnatu'ral "state and in the case of foundry sand, the impurities may include'core oil or'core gum; blackingfcoal and coke dust and fine metal oxides'or 'silicide's.

It hasbeen found thatthe amount of fines in used foundry sand tends "to increase with use and in orderto'render this'sand suitable "for reuse it be'comesne'cessary "to "remove "dirt and fines.

The following analyses give mesh gradings of foundry sand 1) before and (b) after use'and from "thse'fanalyses itwill be seen that the amount of the mesh fractions smaller th'an'90 IMM have increased:

Analysis (a) Analysis Mesh Fraction Mesh Fraction +20 IMM 4.8 +20 IMM 10.1 +30IMM 14;4 +30 IMM 16.1 +4oIMM 5 H140 IMM ;24. 1 1 +60 IMM 33.9 -HSOIMM 28. 2 90 IMM 16.2 +90-IMM '10. 1 +120 IMM 2. 6 +120JIMM 5. 1 +200 IMM 0. 4 +200 IMM 3. 4 200 IMM 0. 2 200 IMM 2.9

- sand, gravel and the" likewhichapparatus eomprises a 'washing vessel, 'afeed "vessel to receive amixture of waterjand' of t "esameto'b'e "washed, a conduit leading from the bottom of the feed vessel into the washing vessel, a -'snan mounted "within-thefeedand washing vessels into theconduitfjoining them, at least one impeller 'witl iin the conduit, a spinner' andan impellerfwithin the Serial No. 39:1;455 1940 washing 'vesselfm'eans forrotating the shaftj at "highspeedand'means for introducing a mixture of water and sand into the feed vessel and for collecting water 'and fines overflowing from the washing vessel and "for "withdrawingheavier particles from the bottom of the washing vessel.

The rate at which water is passed through the apparatus may be controlled so that the suspended matter in the'eiliuent leaving the apparatus may be fiocculated by the process described in British patent specification No. 435,126 or by thense of 'flooculating gels'made in accordance with British patent specificationNo. 516,294, the clarified water being returned to the washing apparatus.

Again, means-maybe employed for deflocculation at the cleaning stage, for example the comparatively small amount of water used at the cleaning stage maycontain a'minute proportion of a'deflocculating'agent. The arrangement may th'erefore'be that at the cleaning stage defiocculation is assisted whereas at the further stage, namely the treatment of the effluent flocculation agents may be used or means for assisting 'fio'cculation.

The'accompanym'g drawing is a diagram in "centralvertical section of a "sand washer embodying' this invention.

1 I is a cylindrical washing vessel with a conical bottom 23 '(Spitzkasten'). Around its upper periphery is a'launder H3 having an outlet. In-

"side theve'ssel II and suitably "supported therein is 'asmall vessel'orconduit 13 in the form of a cylinderor prism opening outat the top into a vessel l2 of larger diameter alsoin the formof a prism'or cylinder and functioning as a feed vessel. At the open bottom of the vessel i3 is a frustoconical base 24 which conveniently takes the form of a partly cylindrical and partly conical vessel embracing the lower part of the vessel l3. Ifhe lower edge of the frustoconical base- 'piece '24 is attached to an annular plate I4 to which are attached two annular'sets of pegs 22 projecting downwardly and arranged in two concentric circles of unequal diameter. The'whole of this plate H! with the pegs 22 and the conical base-piece 24 is adjustable in'relation to'the vessel I3 and can be moved up or down. Below the pegs 22 is an inverted conical spinner I5 supported on the vertical spindle is which has bearings at appropriate positions in the apparatus. The conical spinner l5 has its periphery formed to create a disturbance between the two sets of pegs 22 during the rotation of the spinner 15. Thus the upper periphery of the cone'may have "a'toothed edge as shown. The conical spinner [5 can be driven by appropriate means, for example the shaft l9 may be driven by bevel gearing (and reduction gear if desired) from a motor or from other source of power. Mounted on the shaft [9 are radial impellers I! designed to force the pulp of sand or water radially outwards. The impellers Il may have curved radial blades shrouded above and/or below with annular plates. At the bottom of the shaft I9 is an impeller [6 so designed and arranged as to direct the liquid stream outwardly and upwardly so that the stream due to the impeller l6 tends to cut across the radially outward stream due to the rotation of the spinner [5. 2| is the inlet for the pulp of water and sand to be cleaned.

The method of working is as follows: The contaminated sand, such as used foundry sand, is mixed with water (preferably water which was used before and has been clarified). A freely flowing mixture is used, conveniently one containing about 0.1 to 0.5% of fines, i. e., of particles which will pass a 200 mesh sieve IMM. The mixture is introduced to the vessel l2 through the inlet 2! while the spindle I9 is revolving and the vessel is full of water. When the spinner l5 gets up to speed, the water is forced by the centrifugal action of the blades I1 against the inside of the conduit l3 and its level steadily rises in the vessel l2. It has been found that for the impellers I1 a peripheral speed of about 300 to 600 feet per minute is required. As the sand continues to enter the conduit l3 it is retained there by the centrifugal action until the falling power exceeds a certain figure when the sand discharges into the spinner l5. Here sand is violently thrown outwardly and upwardly between the pegs 22 and finally the washed sand settles out at the bottom of the tank II and is drawn out through the clean sand outlet at the bottom of 23, leaving the fines and impurities to overflow with the water at l8. Normally the volume of overflow would be between and 300 gallons per hour for every square foot of surface. The peripheral speed of the spinner l5 may be of the order of 1100 feet per minute. The spindle l9 may have a speed variable between 50 and 400 R. P. M. In practice a speed of 120 R. P. M. for a spinner diameter of approximately 3 feet and a length for paddles ll of 2 feet are suitable. two functions (1) It creates a swirl in the liquid in the vessel ll so that the sand settling in 23 is in gentle motion and does not pack. (2) By arranging the impeller 16 to create an upward current the lateral orhorizontal current created by the spinner I5 i to some extent neutralised. This upward current assists in ensuring the steady discharge of the lines and impurities to the launder I8.

By the use of the means described and illustrated a washed sand is obtained which has substantially the same characteristics of size and purity as the original sand.

I claim:

1. Apparatus for washing sand, gravel and the like which comprises a washing vessel, a feed vessel arranged above said washing vessel, a conduit connecting the bottom of said feed vessel with the washing vessel, a shaft mounted within the vessel and the conduit, at least one impeller in the conduit, a spinner consisting of a hollow inverted cone having a serrated edge mounted on the shaft in the washing vessel, means for rotating said shaft at high speed, means for admitting a mixture of sand and water The impeller l6 has to the feed vessel, means for collecting water and fines overflowing from the washing vessel and means for drawing 01f heavier particles from the said washing vessel.

2. Apparatus for Washing sand, gravel and the like which comprises a washing vessel provided with a conical bottom, a feed vessel arranged above said washing vessel, a conduit connecting the bottom of said feed vessel with the washing vessel, a shaft mounted within the vessel and the conduit, at least one impeller in the conduit, a spinner consisting of a hollow inverted cone having a serrated edge mounted on the shaft and an impeller in the washing vessel, means for ror tating said shaft at high speed, means for admitting a mixture of sand and water to the feed vessel, means for collecting water and fines overflowing from the washing vessel and means for drawing dff heavier particles from the said washing vessel.

3. Apparatus for washing sand, gravel and the like which comprises a cylindrical washing vessel, having a conical bottom, a cylindrical feed vessel arranged above said washing vessel and coaxial therewith, a cylindrical conduit connecting the bottom of the feed vessel with the washing vessel, an annular plate secured at the end of said conduit, at least one circle of vertically disposed pins secured to said annular plate, a shaft mounted within the vessel and the conduit, at least one impeller in the conduit, a spinner in the washing vessel, said spinner consisting of a hollow inverted cone having a serrated edge and mounted on said shaft, means for rotating said shaft at high speed, means for admitting a mixture of sand and water to the feed vessel, means for collecting water and fines overflowing from the washing vessel and means for drawing ofi heavier particles from the said washing vessel.

4. Apparatus for washing sand, gravel and the like which comprises a washing vessel having a conical bottom and a launder for collecting liquid overflowing from the washing vessel, a feed vessel arranged above the washing vessel and connected thereto by means of a conduit having a frusto conical sleeve adjustably mounted on the end thereof, an annular plate secured to the lower end of said sleeve, two rings of pegs depending from said annular plate, a shaft mounted within the vessel and the conduit, at least one impeller in the conduit, a spinner in the washing vessel, said spinner consisting of a hollow inverted cone having a serrated edge and mounted on said shaft, means for rotating said shaft at high speed, means for admitting a mixture of sand and water to the feed vessel, means for collecting water and fines overflowing from the washing vessel and means for drawing ofi heavier particles from the said washing vessel.

5. Apparatus for washing sand, gravel and the like which comprises a washing vessel having a conical bottom, a feed vessel arranged above said washing vessel and connected thereto by means of a conduit, a frusto conical sleeve adjustably mounted on the lower end of said conduit, a shaft mounted vertically within washing and feed vessels and the-conduit, two impellers mounted on said shaft within the conduit, an impeller mounted at the bottom of the shaft within the washing vessel, a spinner con sisting of a hollow inverted cone having a serrated edge secured to the said shaft, means for rotating said shaft at high speed, at least two rings .of pegs depending from an annular plate secured to the lower end of a frusto conical sleeve adjustably mounted at the lower end of the conduit, means for admitting a mixture of sand and water to the feed vessel, means for collecting water and fines overflowing from the washing vessel and means for drawing oif heavier particles from the said washing vessel.

6. Apparatus for washing sand, gravel and the like which comprises a cylindrical washing vessel having a conical bottom and a launder to receive liquid overflowing from said washing vessel, a cylindrical feed vessel coaxial with the washing vessel and arranged above said washing vessel, a conduit coaxial with said washing and feed vessels and connecting the feed vessel with the washing vessel, a frusto conical sleeve adjustably mounted at the lower end of said conduit, an annular plate secured at the lower end of said sleeve, two concentric rings of pegs depending from said annular plate, a shaft mounted axially in the washing and feed vessels and the conduit, two impellers mounted on said shaft within the conduit, a third impeller mounted at the lower end of the shaft above the conical bottom of the washing vessel, a spinner consisting of a hollow inverted cone having a serrated edge mounted on said shaft below the rings of pegs and means for rotating the shaft at high speed, means for collecting water and fines overflowing from the washing vessel and means for drawing off heavier particles from the said washing vessel.

7. Apparatus for washing sand, gravel and the like which comprises a washing vessel, a feed vessel arranged above said washing vessel, a conduit connecting the bottom of said feed vessel with the Washing vessel, a shaft mounted within the vessel and the conduit, at least one impeller in the conduit, a spinner in the washing vessel, said spinner consisting of a hollow inverted cone having a serrated edge and mounted on said shaft, means for rotating said shaft at high speed so that the impellers have a peripheral speed of the order of 300 to 600 feet per minute and the spinner a peripheral speed of the order of 1100 feet per minute, means for admitting a mixture of sand and water to the feed vessel at a rate between 50 and 300 gallons per hour for every square foot of surface thereof, means for collecting water and fines overflowing from the washing vessel and means for drawing off heavier particles from the said washing vessel.

JOHN OSWALD SAMUEL. 

